Metallocene compounds constitute useful catalyst components for a variety of chemical transformations including olefin polymerizations, where metallocenes are often used in combination with a variety of cocatalysts. It is generally accepted that the metallocene structure itself is intimately involved in determining the physical properties of the resulting polyolefin and hence its eventual usefulness in a variety of end-use applications such as in film, pipe and blow-molded articles. Therefore, there is a need to develop new methods to prepare metallocenes that allow an assortment of substituents to be incorporated into the metallocene structure.
It is likewise of interest to develop new methods to prepare bridged or ansa-metallocene compounds, which comprise two η5-cyclopentadienyl-type ligands linked by a chemical spacer. A variety of substituents can be incorporated into the ansa-metallocene structure, including substituents on the cyclopentadienyl-type ligands, on the bridging group, or both, each of which helps determine the physical properties of polyolefins prepared using these compounds. To accomplish this task, it is also of interest to develop new preparative methods for the ansa-metallocene parent ligand comprising two cyclopentadienyl-type groups linked by a bridging group.